Intradialytic hypotensive episodes, IHE, are among the most frequently occurring complications during dialysis treatment. Intradialytic hypotension can frequently be triggered by rapid liquid withdrawal or incorrectly determined dry weight. A typical reason can be strong reduction of the central blood volume and an inadequate response to such reduction. Numerous algorithms and methods for avoiding such hypotensions have been developed so far. However, it has not been possible to completely avoid intradialytic hypotensive episodes.
From EP 0 956 872 A2 a system of a physiological control loop based on blood pressure comprising a fuzzy controller is known which evaluates blood pressure input values in real time and appropriately sets the ultrafiltration (UF) rate.
When for avoiding intradialytic morbidities by incorporating a physiological control loop a hemodynamic parameter, e.g. either the blood pressure BP or the relative blood volume RBV is controlled, detrimental effects may occur. One drawback of controlling the blood pressure is the patient's impaired well-being due to the large number of blood pressure measurements by means of a cuff. Although the reduction of the number of blood pressure measurements for each therapy solves the problem of frequent blood pressure measurements, another problem is caused, however, as the patient's blood pressure remains unmonitored over rather long periods of time. The relative blood volume can be measured with the aid of an external sensor or a sensor built in the dialyser (e.g. hematocrit sensor) at very short time intervals (<1 s) without any loss of the patient's comfort. Although the relative blood volume is continuously controlled, no correlation to the predialytic, postdialytic and intradialytic blood pressure is shown. Other examinations resulted in the fact that by controlling the relative blood volume a reduction of hypotensive episodes up to 30% can be reached.